1. Field of the Invention
The present invention generally relates to nuclear medicine, and systems for obtaining images of a patient's body organs of interest. In particular, the present invention relates to a mechanism for reducing Field of View truncation in SPECT systems.
2. Description of the Background Art
Nuclear medicine is a unique medical specialty wherein radiation is used to acquire images that show the function and anatomy of organs, bones or tissues of the body. Radiopharmaceuticals are introduced into the body, either by injection or ingestion, and are attracted to specific organs, bones or tissues of interest. Such radiopharmaceuticals produce gamma photon emissions that emanate from the body. One or more detectors are used to detect the emitted gamma photons, and the information collected from the detector(s) is processed to calculate the position of origin of the emitted photon from the source (i.e., the body organ or tissue under study). The accumulation of a large number of emitted gamma positions allows an image of the organ or tissue under study to be displayed.
One type of nuclear imaging system is single photon imaging, or SPECT, relies on the use of a collimator placed in front of a solid state detector, to allow only gamma rays aligned with the holes of the collimator to pass through to the detector. With use of a parallel hole collimator, only rays normal to the face of the detector will pass through to be detected, and therefore smaller detectors will have a more narrowed perimeter of sight.
Solid state detectors offer significant advantage because of their small size, light weight, excellent spatial resolution and compatibility. These advantages enable design freedom for creating more sophisticated geometries to improve imaging resolution for SPECT systems.
Such improved geometries include full or partial ring geometries which have advantages over previous conventional single or dual head systems. However, with such new geometries, collimation becomes more difficult resulting in Field of View (FOV) truncation problems. Truncation occurs when a small modular detector images a relatively large FOV. Due to the parallel hole collimator, when many small solid state detectors form a ring around the FOV, or if one or more detectors orbit the intended FOV, some portions of the FOVE will lie outside the perimeter edge of the detector's line of sight, causing truncation of the image.
One resolution to avoid truncation has been to provide the detector with motion so that the entire FOV can be sampled and the image can then be reconstructed. Drawbacks to this however are that the motion requirement increases system cost as well as potential system error due to positioning inaccuracies and asynchronous motion among the detectors.
Therefore what is needed is a mechanism by which detectors can recover the full FOV efficiently and with high resolution.